1. Field of the Invention
The invention relates to a device for the reading of resistive elements, notably magnetoresistive elements and, especially, magnetoresistive heads arranged in a matrix form.
The invention can be applied, for example to recording on magnetic tapes for computer peripherals, and an object of the invention is the selection and reading of the elements of a multitrack magnetoresistive head with a matrix structure. This device enables the reading, by means of a static head, of several parallel information elements.
2. Description of the Prior Art
Matrix structure magnetoresistive reading heads and their method of selection and reading are described in the French patent applications 2 656 454 and 2 665 010.
These methods operate by associating a preamplifier with each of the rows of heads and, at a given instant, in validating one element in only one of these rows by a selection method applied to the previous column.
In the patent application No. 2 656 454, a non-linearity (saturation of the poles, or angle of the magnetization in the magnetoresistive element) is used.
In the patent application No. 2 665 010, a voltage is applied to the column to be selected, and it is ensured that the current can flow only in the active element of each row, thus leading to the use of an amplifier with low input impedance, such as a transconductance amplifier.
When the resistance of the magnetoresistive elements is low (of the order of 10 ohms or less), as is generally the case with the presently known materials and technologies, the preponderant noise parameter is the noise voltage of the amplifier.
The present invention consists of a method that is better suited to the reading of a matrix of magnetorestrictive sensors, especially when their impedance is low.